Automation Professionals' Advanced Modbus Driver

[woodsb02]

@pturmel

Do you have at least one subscription item on each driver that is polling faster than once per ten seconds? Like many Modbus TCP devices in the wild, my listening server drops idle connections after ten seconds.

Yep - this was the issue.

I didn't have a tag configured on some of the drivers, because I was implementing the redundant modbus solution outlined here:

Indirect OpcItemPath

Kevin beat me to it, here's a brief description on what to do. Your connection names can obviously be whatever you want. For communication between primary and secondary devices with different addresses/hostnames, create 3 device connections Device connection “A” Device connection “B” Device connection “Master” Connections “A” and “B” will only be used for reference to the diagnostics to determine a device connection Tags used throughout the project will reference the “Master” connection A G…

Thanks for the help.

If you're interested - some suggestions of how this dropping of idle connections could be made more user friendly:

1. Make this user configurable in the modbus server - enable/disable whether to drop idle connections or not, and configurable time after which they should be dropped.
2. Describe the feature in the documentation
3. Create a log entry when an idle session is dropped